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Research Papers: Flows in Complex Systems

A Method to Generate Propulsor Side Forces

[+] Author and Article Information
Stephen A. Huyer1

Naval Undersea Warfare Center, Code 8233, Building 1302/2, Newport, RI 02874stephen.huyer@navy.mil

Amanda Dropkin, James Dick, David Beal

Naval Undersea Warfare Center, Code 8233, Building 1302/2, Newport, RI 02874

1

Corresponding author.

J. Fluids Eng 132(2), 021101 (Feb 03, 2010) (9 pages) doi:10.1115/1.4000745 History: Received October 24, 2008; Revised November 25, 2009; Published February 03, 2010; Online February 03, 2010

Abstract

A computational study was performed to investigate a method to generate vehicle maneuvering forces from a propulsor alone. A ducted, preswirl propulsor was configured with an upstream stator row and downstream rotor. During normal operation, the upstream stator blades are all situated at the same pitch angle and preswirl the flow into the propulsor while generating a roll moment to counter the moment produced by the rotor. By varying the pitch angles of the stator blade about the circumference, it is possible to both generate a mean stator side force and subsequently vary the axial velocity and swirl that is ingested into the propulsor. The rotor then generates a side force in response to the inflow. Both potential flow and fully viscous 3D Reynolds averaged Navier–Stokes (RANS) computations were used to predict the stator forces, velocity field, and rotor response. Potential flow methods were used for initial examination of a wide variety of stator configurations. The most promising were then modeled using RANS. The RANS inflow was then computed and used as velocity boundary conditions during rotor blade design using potential flow methods. Blade parameters including blade number, rake, skew, and a combination of the two were varied to characterize their effects. RANS was used to then validate the final propulsor design. Computations demonstrated that total side force coefficients on the order of 0.1 and moment coefficients about the stator leading edge of 0.066 could be generated by the propulsor alone. This translates to an additional 50% control authority at 3 kn for current Navy $21″$ unmanned undersea vehicles.

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Figures

Figure 2

Vortex lattice of the stator blade row and wake on the first blade with the main body (not including the nose region)

Figure 3

Tangential velocity distributions normalized by the freestream velocity at span locations from 0.58 to 0.94

Figure 4

Tangential velocity distributions normalized by the freestream velocity for eight- and 12-blade stator rows for a range of pitch amplitudes A

Figure 5

Drag coefficient convergence with increased grid resolution

Figure 6

FLUENT ® calculations highlighting the axial velocity distributions (normalized by the freestream velocity) in the rotor inflow plane (x/Rrotor=0.75) due to the eight-blade stator row

Figure 7

FLUENT ® calculations highlighting the tangential velocity distributions (normalized by the freestream velocity) in the rotor inflow plane (x/Rrotor=0.75) due to the eight-blade stator row

Figure 8

FLUENT ® calculations highlighting the axial and tangential velocity distributions (normalized by the freestream velocity) in the rotor inflow plane (x/Rrotor=0.75) due to the 12-blade stator row for A=15 deg

Figure 1

FLUENT surface mesh depicting the body and stator geometries

Figure 9

FLUENT ® predictions of the mean propulsor force coefficients produced by the stator blade row with hull and duct influences. MPUF calculations shown for comparison are for the blades only.

Figure 10

Baseline, rake, skew, and rake and skew rotor geometries

Figure 11

Unsteady side force coefficients for varying stator pitch amplitudes A. Forces are for the Rake/Rrotor=0.4, 30 deg skew, nine-blade rotor configuration

Figure 12

Mean y- and z-force coefficients as a function of the blade number for the range of rakes examined

Figure 13

Mean y- and z-force coefficients as a function of the blade number for the range of skews examined

Figure 14

Mean y- and z-force coefficients as a function of the blade number for a constant skew of 30 deg for rake values of 0.1, 0.2, 0.3, and 0.4

Figure 15

Rms force magnitude coefficients as a function of blade number examining the effect of skew (zero rake, (a)) and rake (30 deg skew, (b))

Errata

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